The Rise of Solar Cycle 24: Magnetic Fields from the Dynamo through the Photosphere and Corona and Connecting to the Heliosphere Part 1: Interior and Photosphere

Subsurface Flows: Torsional Oscillation (east-west) variation from the mean differential rotation very small signal related to the timing of the cycle Meridional Flow (north-south) important for the timing of the cycle Frank Hill: observations Mark Miesch : modeling interpretation

Torsional oscillation at a depth of 7 Mm Cycle 25??? 2019?-2030? Cycle 23 (1995-2008) Equatorward Branch Cycle 24 (2008-2019?) Poleward branch Equatorward branch 5 m/s -5 m/s No sign yet of poleward branch flow for Cycle 25. May mean that Cycle 25 will not start until at least 2023

M. Rempel suggested that the non-appearance of the high-latitude branch may be due to a change in the differential rotation profile that arises from a reduction of the  effect Strong cycles have more rigid differential rotation (magnetic tension tends to reduce rotation shear) Weak cycles rotate more differentially, i.e. poles slow down BUT Plot had a mean differential rotation subtracted this may mask poleward branch This hypothesis can be tested Stay tuned for the next NSO press release !!!

Meridional Flow At the Surface: both heliosesimology and correlation tracking techniques show it poleward + AR band modulation hard to measure at high latitudes multiple cells in latitude faster (1-2 m/s) flow near surface during recent minimum Deep meridional flow: hard to measure issues with data inversions seems to increase with depth complex cell return flow not detected

In contrast, using correlation tracking techniques : David Hathaway finds that the meridional flow decreases with depth and there is a shallow return flow R. Komm: reliable technique but no agreement on interpretation (longer time scales do not necessarily mean longer-lived cells) data may not indicate a shallow return flow! What is important for the dynamo model is the return flow at the bottom of the convection zone which has not been detected yet Consensus: We do not know much about meridional flow, especially its variation with depth

magnetic flux emergence Gordon Petrie: magnetic flux emergence first spot Jan 2008 30deg latitude

strong recovery after very deep minimum current activity Number of images with fields stronger than 1 kG Cycle 21 Cycle 22 Cycle 23 Cycle 24 strong recovery after very deep minimum current activity level <50% of Cycle 21-23 maxima in terms of maximum field strength

magnetic butterfly covering 37 years of NSO data !!! long minimum Cycle 21 Cycle 22 Cycle 23 Cycle 24 hemispheric asymmetry: south more active at the end of cycle 23 north more active at the start of cycle 24, still more active now not seen in the preceding cycles but cycle 20 shows noticeable asymmetry

POLAR MAGNETIC FIELDS weak polar magnetic fields (consistent with the observed decrease in open flux in the heliosphere) A. Munoz-Jaramillo: how important are polar fields for the dynamo? Are they a by-product or the seeds for the next cycle(s)? This is also important for the heliosphere-dynamo connection

Doug Biesecker: challenged the observational evidence that we are entering a Maunder Minimum Weakening Magnetic Fields in Sunspot What was in the press release The raw data presented at Space Weather Workshop 2010 no obvious reason that a straight line is the appropriate fit to these data. A curve that follows the solar cycle may in fact provide a better reduced chi square. Solar Max Solar Min

The slowing ‘rush to the poles’ Cycle 24 started ‘late.’ Cycle 23 was 12 years long, 2 years longer than the previous two cycles. Iron emission seems to appear right as expected, 12 years after the last one Cycle 21 (10.3 yrs) Cycle 22 (10.0 yrs) Cycle 23 (12.2 yrs)

The Rise of Solar Cycle 24 Part 2: Corona & Heliosphere 9:45-11:00: polar fields (Dick Altrock) 11:30-12:45: open flux (Janet Luhmann & Nathan Schwadron) 14:00-17:00: open flux & heliosphere (cont.)

The Rise of Solar Cycle 24 Part 2: Corona & Heliosphere we will be in room Cabaret today we hope you will join us!